Hydrophilic DLC on substrate with UV exposure

ABSTRACT

A substrate is coated with a layer(s) or coating(s) that includes, for example, amorphous carbon in a form of diamond-like carbon (DLC). In certain embodiments, the DLC inclusive layer may be doped with at least one polar inducing dopant (e.g., Boron, Nitrogen, and/or any other suitable polar inducing dopant) in order to make the layer more polar and thus more hydrophilic so as to have a lower contact angle θ. In other embodiments, where such doping is optional, the DLC may be exposed to ultraviolet (UV) radiation in a manner sufficient to cause the contact angle θ of the DLC layer to drop into a hydrophilic range (e.g., less than or equal to about 20 degrees).

[0001] This is a continuation-in-part (CIP) of U.S. patent applicationSer. No. 09/899,176, filed Jul. 5, 2001, which is a division of U.S.patent application Ser. No. 09/577,337, filed May 24, 2000 (now U.S.Pat. No. 6,303,225), the disclosures of which are hereby incorporatedherein by reference.

[0002] This invention relates to a hydrophilic coating includingdiamond-like carbon (DLC) provided on (directly or indirectly) asubstrate of glass, plastic, or the like, and a method of making thesame. More particularly, this invention relates to a DLC inclusivecoating that is exposed to at least ultraviolet (UV) radiation in orderto cause the coating to either become hydrophilic or become morehydrophilic (i.e., to cause contact angle θ of the coating to decrease).

BACKGROUND OF THE INVENTION

[0003] It is often desirable to provide a hydrophilic coating (e.g.,anti-fog coating) on a substrate such as an automotive windshield,automotive window, automotive mirror, architectural mirror, bathroommirror, or the like. Such coatings may reduce the likelihood of waterdrops deposited on the substrate taking globular shape(s), therebyenabling visibility to be improved. In other words, hydrophilic coatingsfunction to reduce bead-like condensation on substrate surfaces (e.g.,on the interior surface of an automotive windshield or window). Ahydrophilic coating can reduce the formation of many tiny droplets ofliquid, which can scatter light, on a surface (i.e., make condensationon a surface film-wise as opposed to droplet-wise).

[0004] Unfortunately, certain hydrophilic coatings are not as durableand/or hard as would otherwise be desired and thus are not efficientfrom a practical point of view for applications such as automotivewindshields and/or other types of windows.

[0005] In view of the above, it is apparent that there exists a need inthe art for (i) a coated article (e.g. coated glass or plasticsubstrate) having hydrophilic properties, and a method of making thesame, and/or (ii) a protective hydrophilic coating for window and/ormirror substrates that is somewhat resistant to scratching, damage, orthe like.

[0006] It is a purpose of different embodiments of this invention tofulfill any or all of the above described needs in the art, and/or otherneeds which will become apparent to the skilled artisan once given thefollowing disclosure.

SUMMARY OF THE INVENTION

[0007] An object of this invention is to provide a durable coatedarticle that it is less likely to attract or be affected by bead-likeliquid condensation. Exemplary applications to which such hydrophiliccoating(s) may be applied include, for example without limitation,automotive windshields, automotive backlites (i.e., rear vehiclewindows), automotive side windows, architectural windows, mirrors, etc.

[0008] Another object of this invention is to provide a scratchresistant hydrophilic coating for use in conjunction with a coatedarticle.

[0009] Another object of this invention is to form or provide ahydrophilic coating by doping diamond-like carbon (DLC) with at leastone polar inducing dopant(s) such as, for example, boron (B) and/ornitrogen (N). In certain embodiments, the atomic percentage of the polarinducing dopant(s) (e.g., B and/or N dopants, but not including Hdopants that may or may not be added because H is not a polar inducingdopant) is no greater than about 10%, more preferably no greater thanabout 5%, and most preferably no greater than about 4%. A polar inducingdopant is a dopant that causes DLC to become more graphitic (e.g., causemore sp² bonds), as opposed to more tetrahedral (i.e., more sp³ bonds).Polar inducing dopant(s) tend to cause the DLC inclusive layer to bemore polar, which in turn increases surface energy and thus provides fora more hydrophilic coating.

[0010] Another object of this invention is to provide a coated article,wherein a layer of the coating includes both sp² and sp³ carbon-carbonbonds and has a wettability W with regard to water of at least about 700mN/m, more preferably at least about 750 mN/m, and most preferably atleast about 800 mN/m. This can also be explained or measured in Joulesper unit area (mJ/m²).

[0011] Another object of this invention is to cause contact angle θ of aDLC inclusive layer or coating to decrease due to ultraviolet (UV)exposure. The contact angle before such exposure may or may not behydrophilic, but after said exposure in certain example embodiments thepost-UV contact angle θ is less than about 20 degrees, more preferablyless than about 15 degrees, even more preferably less than about 10degrees, and even more preferably less than about 8 degrees.

[0012] Another object of this invention is to provide a coated article,wherein a layer of the coating includes both sp² and sp³ carbon-carbonbonds and has a surface energy Υ_(c) of at least about 24 mN/m, morepreferably at least about 26 mN/m, and most preferably at least about 28mN/m.

[0013] Another object of this invention is to provide a coated article,wherein a DLC inclusive layer of the coating has an initial (i.e. priorto being exposed to environmental tests, rubbing tests, acid tests, UVtests, or the like) water contact angle θ of no greater than about 10degrees, more preferably no greater than about 8 degrees, even morepreferably no greater than about 6 degrees, and most preferably nogreater than about 4 degrees. The article's initial contact angle θ maybe as low as 1-3 degrees in certain embodiments. In certain embodimentsthe article's contact angle may increase over time upon exposure toenvironmental elements (as graphitic sp² C—C bonds wear off) while inother embodiments the article's contact angle may decrease over timeupon such exposure.

[0014] Another object of this invention is to provide a hydrophilic DLCinclusive layer for coating a substrate. In at least one portion of thelayer no more than about 70% of the bonds in that portion of the layerare of the sp³ type, and more preferably no more than about 60% of thebonds are of the sp³ type. A substantial portion of the remainder of thebonds may be of the graphitic or sp² type. The bonds in the layer mayinclude, for example, carbon-carbon (C—C) bonds, carbon-nitrogen (C—N)bonds, carbon-boron (C—B) bonds, and/or carbon-hydrogen (C—H) bonds. Thesp³ type bonds (e.g., C—C bonds) function to increase the hardness andscratch resistance of the coating, while the graphitic sp² type bonds(e.g., C—C, C—N and/or C—B bonds) cause the coating to be morehydrophilic and have a lower contact angle.

[0015] Another object of this invention is to provide a coating whichcan make accumulated condensation form in a more film-wise manner; asopposed to a droplet-wise manner.

[0016] Still another object of this invention is to form amine (NH₂)functional groups near the surface of a hydrophobic coating or layer soas to enhance hydrophilicity.

[0017] Yet another object of this invention is to fulfill one or more ofthe above listed objects and/or needs.

[0018] Certain example embodiments of the instant invention fulfill oneor more of the above-listed objects or needs by providing a coated glassarticle comprising:

[0019] a glass substrate;

[0020] a layer comprising diamond-like carbon (DLC) with sp³carbon-carbon bonds provided on said glass substrate; and

[0021] wherein said layer comprising DLC is ultraviolet (UV) radiationexposed so as to cause the layer to have a contact angle θ with a dropof water thereon of no greater than about 20 degrees.

[0022] Other example embodiments of the instant invention fulfill one ormore of the above-listed objects or needs by providing a method ofmaking a coated article, the method comprising:

[0023] ion beam depositing a diamond-like carbon (DLC) inclusive layeron a substrate; and

[0024] exposing the DLC inclusive layer to ultraviolet (UV) radiation ina manner sufficient to cause a contact angle θ of the DLC inclusivelayer to decrease by at least about 20%.

[0025] Still further example embodiments of the instant inventionfulfill one or more of the above-listed objects and/or needs byproviding a coated article comprising a DLC inclusive layer supported bya glass substrate, wherein the DLC inclusive layer has a contact angle θless than or equal to 10 degrees.

[0026] This invention will now be described with respect to certainembodiments thereof, along with reference to the accompanyingillustrations.

IN THE DRAWINGS

[0027]FIG. 1 is a side cross sectional view of a coated articleaccording to an embodiment of this invention, wherein a glass or plasticsubstrate is provided with a hydrophilic coating thereon including a DLCinclusive layer.

[0028]FIG. 2 is a side cross sectional view of a coated articleaccording to another embodiment of this invention, wherein a glass orplastic substrate is provided with a hydrophilic coating thereonincluding a DLC inclusive layer.

[0029]FIG. 3 is a side cross sectional view of a coated articleaccording to another embodiment of this invention, wherein a glass orplastic substrate is provided with a hydrophilic coating thereonincluding a DLC inclusive layer.

[0030]FIG. 4 is a side cross sectional partially schematic viewillustrating a contact angle θ of a drop (e.g., sessile drop of water)on an uncoated glass substrate.

[0031]FIG. 5 is a side cross sectional partially schematic viewillustrating a high contact angle θ of a drop on a coated articleincluding a hydrophobic coating of, for example, an article disclosed inrelated application Ser. No. 09/442,805.

[0032]FIG. 6 is a side cross sectional partially schematic viewillustrating a low contact angle θ of a drop (e.g., sessile drop ofwater) on a coated article according to an embodiment of this invention.

[0033]FIG. 7 is a side cross sectional view of a linear ion beam sourcewhich may be used in any embodiment of this invention for depositing aDLC inclusive hydrophilic layer(s).

[0034]FIG. 8 is a perspective view of the linear ion beam source of FIG.7.

[0035]FIG. 9 is a flowchart illustrating steps taken according toanother embodiment of this invention where a DLC inclusive layer isexposed to ultraviolet (UV) light/radiation in order to lower contactangle θ thereof.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THIS INVENTION

[0036] Referring now more particularly to the accompanying drawings inwhich like reference numerals indicate like elements throughout theaccompanying views.

[0037] Certain embodiments of this invention relate to improvinghydrophilic qualities of a coated article (e.g., automotive windshield,automotive backlite, automotive side window, snow-mobile windshield,architectural window, mirror, etc.) by providing a diamond-like carbon(DLC) inclusive layer or coating on a substrate in a manner such thatthe resulting article and/or layer has hydrophilic qualities orcharacteristics. One way of providing DLC with hydrophiliccharacteristics has been found to be by doping DLC with at least onepolar inducing dopant (e.g., Nitrogen (N), Boron (B), and/or any othersuitable polar inducing dopant), the DLC inclusive layer may be mademore polar so as to have a higher surface energy and thus be morehydrophilic.

[0038] In other embodiments of this invention, a DLC inclusive layer(e.g., having a contact angle θ from 5-100 degrees) may be exposed toultraviolet (UV) radiation in order to lower the contact angle θ of theDLC inclusive layer to, for example, a hydrophilic range. Optionally,the DLC inclusive layer may be exposed to water at the same time as theUV exposure in order to speed up the process of contact angle θreduction. The UV exposure embodiment may be used either in combinationwith, or separately from, the aforesaid doping embodiment in order toprovide a hydrophilic coating.

[0039] In doping embodiments of this invention, the provision of the atleast one polar inducing dopant increases the polar component of the DLCinclusive layer's surface energy, which in turn increases the layer'stotal surface energy. The higher the surface energy, the morehydrophilic the layer and the lower the contact angle θ. Thus, byincreasing the surface energy via the dopant(s), the hydrophilicity canbe improved and thus the contact angle θ can be lowered.

[0040] Combining the hydrophilicity with the use of an amorphousdiamond-like carbon (DLC) layer/coating provided on the base substrateenables the resulting coated article to have a low contact angle θ aswell as surface hardness and scratch resistant characteristicssufficient such that the article may be used in automotive and otherhigh exposure environments where durability is desired.

[0041]FIG. 1 is a side cross-sectional view of a coated articleaccording to an embodiment of this invention, wherein at least onediamond-like carbon (DLC) inclusive protective coating(s) or layer 3 isprovided on substrate 1. The coated article has an exterior or outersurface 9. Substrate 1 may be of glass, plastic, ceramic, or the like.

[0042] In doping embodiments, layer or coating 3 includes at least onepolar inducing dopant therein which causes bonds in the DLC inclusivelayer to be more polar, which in turn causes a higher surface energy andlower contact angle θ. The dopant(s) cause more graphitic or polar sp²type bonds (e.g., C—C sp² type bonds, C—N sp² type bonds, and/or C—B stype bonds) to be formed in layer 3 so that the layer includes both sp²type and sp³ type (e.g., C—C sp³ type) bonds. When more bonds in layer 3become polar, this results in water being more attracted to the layer 3since water is polar. The tetrahedral amorphous sp³ type C—C bonds(ta-C) provide the layer 3 with acceptable hardness and/or scratchresistance characteristics while the sp² type C—C and C-dopant bondsimprove the layer's hydrophilicity. Preferably, a substantial portion ofthe carbon in layer 3 is in amorphous or disordered form (as opposed tocrystalline form for example).

[0043] The dots in layer/coating 3 in FIG. 1 illustrate the dopant,which is shown as being relatively evenly or uniformly distributedthroughout the thickness of layer 3. As evident from the above,exemplary polar-inducing dopants include, but are not limited to,Nitrogen (N), Boron (B), Phosphorous (P), As, S, Sb, Ga, In, and thelike. Dopants such as N and B may be used either alone or in combinationto dope the DLC inclusive layer 3 in certain embodiments so as toimprove the layer's hydrophilicity. Layer 3 functions in a hydrophilicmanner (i.e. it is characterized by low contact angles θ and/or highsurface energies) so as to reduce the occurrence of bead-likecondensation forming on the coated article. Hydrophilic characteristicsmay be advantageous in environments such as bathroom mirror surfaces,interior surfaces of automotive windshields or windows, and the like.

[0044] In UV exposure embodiments (which may be carried out incombination with doping embodiments, or without doping), DLC inclusivelayer 3 may or may not have the aforesaid dopant(s) therein. Moreparticularly, in UV exposure embodiments, the DLC inclusive layer 3 asdeposited may be hydrophilic, or may be non-hydrophilic (i.e., layer 3as deposited may have a contact angle θ of any value from 5-100degrees). Exposure of the layer 3 to UV radiation (and optionally water)causes the contact angle of the layer 3 to decrease (e.g., tohydrophilic range(s)). Thus, following a significant amount of UVexposure, the contact angle θ of the DLC inclusive layer 3 in UVexposure embodiments is preferably less than about 20 degrees, morepreferably less than about 15 degrees, even more preferably less thanabout 10 degrees, and most preferably less than about 8 degrees.

[0045] In certain embodiments, hydrophilic layer 3 may be from about 10to 1,000 Angstroms thick, more preferably from about 50 to 200 Angstromsthick. In one exemplary embodiment, layer 3 may be about 100 Angstromsthick. Moreover, in certain exemplary embodiments of this invention,layer 3 has an average hardness of at least about 10 GPa, morepreferably of at least about 20 GPa, even more preferably of at leastabout 50 GPa, and most preferably from about 50-600 GPa. In certainembodiments, layer 3 may have an average hardness of about 75 GPa. Layer3 preferably has good abrasion resistance, a coefficient of friction offrom about 0.05 to 0.20 (e.g., 0.15), and an average surface roughnessof no greater than about 0.3 nm. Because of the presence of both the sp²type and sp³ type bonds in layer 3, the layer preferably has a densityof at least about 2.4 grams/cm² (more preferably from about 2.5 to 3.0grams/cm²). Layer 3 is preferably corrosion resistant, even in thecontext of significant humidity and/or heat. Layer 3 may also be inertto acids, alkalis, solvents, salts, and/or water in certain embodimentsof this invention. Thus, layer 3 may act as a barrier to chemicalattacks on the underlying substrate 1 (e.g., a soda-lime-silica glasssubstrate).

[0046] Hydrophilic layer 3 has one surface exposed to the air or theatmosphere. In doping embodiments, layer 3 after it has been doped tomake it more hydrophilic, has a much lower contact angle θ with asessile drop of water than it otherwise would without doping. In certaindoping embodiments of this invention, layer 3 has an initial contactangle θ with a sessile drop of water of no greater than about 10degrees, more preferably of no greater than about 8 degrees, even morepreferably of no greater than about 6 degrees, and most preferably nogreater than about 4 degrees. In certain embodiments, the contact anglemay be as low as 1-3 degrees. As mentioned above, in certain UV exposureembodiments, the contact angle of layer 3 may be brought down from anon-hydrophilic range into a hydrophilic range upon exposure of thelayer to significant UV rays.

[0047] In certain doping embodiments of this invention, the amount ofpolar inducing dopant material (one or more dopants) in hydrophiliclayer 3 is from about 1-30%, atomic percentage, more preferably fromabout 1-10%, even more preferably from about 1-5%, and most preferablyfrom about 1-4%. In certain embodiments, polar inducing dopant(s) inlayer 3 may represent about 3-4% (atomic) of the atoms in layer 3. Theremainder may be C and/or H in certain embodiments. In certaininstances, it has been found that increasing the dopant percentage bytoo much can decrease the diamond like properties of the layer 3, makingthe layer too graphitic for practical applications in certaincircumstances (e.g., the more graphitic the coating the darker and lesstransmissive/transparent it becomes). Since the DLC inclusive layer 3 isonly doped with low amounts of polar inducing dopant(s) such as B and/orN, much of the diamond-like nature of the bonding in layer 3 ispreserved. Other types of dopant (e.g., H is not a polar inducingdopant) may or may not be provided in layer 3 in certain embodiments.

[0048] Thirteen exemplary make-ups of a doped hydrophilic layer 3 areset forth below in Chart No. 1, these exemplary make-ups beingapplicable to any doping embodiment herein including any of theembodiments of FIGS. 1-3. CHART NO. 1 Polar Atomic % C Atomic % N Atomic% B Component Atomic % H 97 1.5 1.5  6 0 97 2.1 0.9 10 0 96 3.0 1.0  7 087 2.1 0.9 — 10.0 89 2.0 1.0 — 8.0 96 4.0 0.0 — 0 97 0 3.0 — 0 70 10.0 0— 20.0 75 0 5.0 — 20.0 71 7 0 — 22.0 69 6 0 — 25.0 68 0 8 — 24.0 67 9 0— 25.0

[0049] Layers or films 3 doped independently with either N or B havebeen found to be hydrophilic. However, it has also been found thatadditional surprising hydrophilic properties may result when a mixtureof dopants (e.g., N and B) is used to dope DLC inclusive layer 3. Incertain embodiments, the ratio of N to B may be approximately 2:1 (N:B).Other dopants may of course be used; and in UV exposure embodimentsdopants are optional.

[0050] Optical characteristics of layer 3, such as n & k refractiveindices, and Tauc optical bandgap, can be tailored/adjusted by changingthe concentration or percentage of dopants (e.g., N and/or B) in thelayer/film. The optical bandgap may be varied between 1.75 and 3.2 eV incertain embodiments. The “n” refractive index at 550 nm may be variedbetween, for example, 1.6 and 2.3, while the “k” refractive index at 550nm may be varied between, for example, 0.01 and 0.1 in certainembodiments (permittivity at GHz 4.7). In certain embodiments, a highbandgap (e.g., above 3 eV) and/or an absorption coefficient greater thanabout 10⁶ cm⁻¹ implies that such films/layers 3 are ultraviolet (UV)absorbing. Strong binding energy also implies strong UV radiationresistance. In certain embodiments, UV transmission of layer 3 at 350 nmis no greater than about 40% (preferably no greater than about 35%).

[0051] In FIG. 1 doping embodiments, the dopant(s) may be distributed ina fairly uniform manner throughout the thickness of layer 3, asillustrated. For example, dopant inclusive gas may be provided in an iondeposition apparatus throughout the entire course of the depositionprocess for layer 3.

[0052] In the FIG. 2 embodiment, the dopant(s) is/are not uniformlydistributed throughout the entire thickness of hydrophilic layer 3.Instead, a more significant portion of dopant(s) is provided near theexterior surface of layer 3 than near the interface between layer 3 andsubstrate 1, as shown in FIG. 2. The presence of the dopant(s) at ornear the exterior surface of layer 3 enables the bonds near the layer'ssurface to be more graphitic. Thus, layer 3 still has the hydrophilicproperties described herein (e.g., low contact angle(s). For example, incertain embodiments the outermost 10 angstrom (A) thick portion (or 10nm thick portion in other embodiments) of layer 3 may include at leastabout 3% dopant atoms (e.g., N, B, P, As, Sb, Ga, and/or In), morepreferably at least about 5%, and most preferably at least about 7%. Theprovision of these polar inducing dopant atoms near the coating'ssurface results in a more polar coating surface. The rest of layer 3(i.e., the middle of layer 3 and/or the portion of layer 3 adjacent thesubstrate or some intermediate layer) may be of or include undoped DLCin certain embodiments, or alternatively may be of or include DLC dopedwith Si, O, or H. This enables many of the graphitic sp² type bonds tobe located at or near the exterior surface of layer 3. Too many sp² typebonds in layer 3 can undesirably reduce its transparency or transmissioncharacteristics, so in some embodiments it may be desirable to minimizethe presence of sp² type bonds at locations other than at or near theexterior surface where they are needed to lower the contact angle θ ofthe layer 3.

[0053] In an exemplary embodiment of this invention (see the tenthlisted exemplary make-up listed above in Chart No. 1), where the C isdoped with N and H, it has been found that the provision of the N causesamine (NH₂) functional groups to be formed at or near the surface oflayer 3. In such amine groups, for example, one of the N bonds is with aC (sp²) while the other two N bonds are with H. These amine groupsenhance the hydrophilic nature of the layer 3 and thus of the coatedarticle. In exemplary amine inclusive embodiments, the layer may includefrom about 60-84% C, from about 1-12% B, and from about 4-39% H(atomic); and more preferably from about 65-75% C, from about 5-10% B,and from about 15-30% H.

[0054]FIG. 3 illustrates that in certain embodiments of this invention,at least one intermediate layer 2 may be provided between substrate 1and the one or more hydrophilic layer(s) 3. Thus, both layer(s) 3 andlayer(s) 2 are deposited on, and provided on, substrate 1 in thisembodiment. Any desired layer may be utilized as an intermediate layer2. For example, intermediate layer 2 may include a low-E layeringsystem, another DLC inclusive layer, a silicon oxide layer, a siliconnitride layer, and/or a titanium oxide layer in certain embodiments ofthis invention. The term “on” (with regard to a layer being “on” asubstrate or other layer) herein means supported by, regardless ofwhether or not other layer(s) are provided therebetween. Thus, forexample, DLC inclusive layer 3 may be provided directly on substrate 1as shown in FIGS. 1-2, or may be provided on substrate 1 with a low-E orother layer(s) therebetween as shown in FIG. 3. Exemplary layer systems(in full or any portion of these coatings) that may be used as low-E orother coating(s) 2 on substrate 1 between layer 3 and the substrate areshown and/or described in any of U.S. Pat. Nos. 5,837,108, 5,800,933,5,770,321, 5,557,462, 5,514,476, 5,425,861, 5,344,718, 5,376,455,5,298,048, 5,242,560, 5,229,194, 5,188,887 and 4,960,645, which are allhereby incorporated herein by reference.

[0055] In certain embodiments, in at least one portion of DLC inclusivelayer 3 no more than about 70% of the bonds in the layer are of the sp³type, and more preferably no more than about 60% of the bonds in thelayer are of the sp³ type, so that this portion of the layer may attainhydrophilic characteristics. In certain preferred embodiments, no morethan about 50% of the bonds in layer 3 are of the sp³ type (e.g., sp³type C—C bonds), or in other embodiments this may be the case only nearthe exterior or outer surface of layer 3. A substantial portion of theremainder of the bonds are of the graphitic or sp² type. The bonds inthe layer may include, for example, carbon-carbon (C—C) bonds,carbon-nitrogen (C—N) bonds, carbon-boron (C—B) bonds, and/orcarbon-hydrogen (C—H) bonds. The sp³ type bonds (e.g., C—C bonds)function to increase the hardness and scratch resistance of the coating,while the graphitic sp² type bonds (e.g., C—C, C—N and/or C—B bonds)cause the coating to be more hydrophilic and have a lower contact angle.It has been found that different techniques may be used to increase thenumber of graphitic sp² type bonds, including but not limited to a)doping as discussed herein, b) heating up the underlying substrateduring the layer 3 deposition process, and/or c) utilizing a higher ionenergy eV energy during the layer 3 deposition process (e.g., from about200-600 eV, most preferably from about 375 to 425 eV). Also, the aminefunctional groups discussed above may also function to enhance thehydrophilic nature of the article. A higher eV energy used during theion deposition process of layer 3 results in less sp³ type bonds andmore sp² type bonds. Techniques b) and/or c) may be used in combinationwith the doping herein to obtain hydrophilic characteristics.

[0056] In certain embodiments, DLC inclusive layer 3 and/or the coatingsystem on substrate 1 is/are at least about 75% transparent to ortransmissive of visible light rays, preferably at least about 85%, andmost preferably at least about 95%.

[0057] When substrate 1 is of glass, the glass may be from about 1.5 to5.0 mm thick, preferably from about 2.3 to 4.8 mm thick, and mostpreferably from about 3.7 to 4.8 mm thick. Conventional soda lime silicaglass may be used as substrate 1 in certain embodiments, such glassbeing commercially available from Guardian Industries, Corp., AuburnHills, Mich. In certain other embodiments of this invention, substrate 1may be of borosilicate glass, or of substantially transparent plastic.In still further embodiments, an automotive window (e.g. windshield,backlite, or side window) including any of the above glass substrateslaminated to a plastic substrate may combine to make up substrate 1,with a coating system of any of FIGS. 1-3 provided on a surface of sucha substrate to form the window. In other embodiments, substrate 1 mayinclude first and second glass sheets of any of the above mentionedglass materials laminated to one another, for use in window (e.g.automotive windshield, residential window, commercial architecturalwindow, automotive side window, vacuum IG window, automotive backlite orback window, etc.) and/or other environments.

[0058] When substrate 1 of any of the aforesaid materials is coated withat least DLC inclusive layer 3 according to any of the FIGS. 1-3embodiments, the resulting coated article has the followingcharacteristics in certain example non-limiting embodiments: visibletransmittance (Ill. A) greater than about 60% (preferably greater thanabout 70%, and most preferably greater than about 80%), UV (ultraviolet)transmittance less than about 38%, total solar transmittance less thanabout 45%, and IR (infrared) transmittance less than about 35%(preferably less than about 25%, and most preferably less than about21%). Visible, “total solar”, UV, and IR transmittance measuringtechniques are set forth in U.S. Pat. No. 5,800,933.

[0059] Hydrophilic performance of coating/layer 3 in any of the aboveembodiments is a function of contact angle θ, surface energy Υ, and/orwettability or adhesion energy W. The surface energy Υ of layer 3 may becalculated by measuring its contact angle θ. Exemplary contact angles θare illustrated in FIGS. 4-6. A hydrophilic coating or layer system 3according to an embodiment of this invention is on the substrate of FIG.6, while no coating of any kind is on the substrate of FIG. 4 and ahydrophobic coating is on the substrate of FIG. 5. No coatings areillustrated in FIGS. 4 and 6 for purposes of simplicity. To measurecontact angle in one embodiment, a sessile drop 31 of a liquid such aswater is placed on the substrate as shown in FIGS. 4-6. A contact angleθ between the drop 31 and underlying article appears, defining an angleθ depending upon the interface tension between the three phases at thepoint of contact. The contact angle is greater in FIG. 5 than in FIG. 4,because the coating layer on the substrate in FIG. 5 is hydrophobic(i.e., results in a higher contact angle). However, due to thisinvention, the contact angle θ in FIG. 6 is much lower than in either ofFIGS. 4-5.

[0060] Generally, the surface energy Υ_(c) of a layer 3 or any otherarticle/layer can be determined by the addition of a polar and adispersive component, as follows: Υ_(c)=Υ_(CP)+Υ_(CD), where Υ_(CP) isthe layer's/coating's polar component and Υ_(CD) the layer's/coating'sdispersive component. The polar component of the surface energyrepresents the interactions of the surface mainly based on dipoles,while the dispersive component represents, for example, van der Waalsforces, based upon electronic interactions. Generally speaking, thehigher the surface energy Υ_(c) of layer 3, the more hydrophilic thelayer (and coated article) and the lower the contact angle θ.

[0061] Adhesion energy (or wettability) W can be understood as aninteraction between polar with polar, and dispersive with dispersiveforces, between the exterior surface 9 of the coated article and aliquid thereon such as water. Υ^(P) is the product of the polar aspectsof liquid tension and article tension; while Υ^(D) is the product of thedispersive forces of liquid tension and article tension. In other words,Υ^(P)=Υ_(LP)*Υ_(CP); and Υ^(D)=Υ_(LD)*Υ_(CD); where Υ_(LP) is the polaraspect of the liquid (e.g. water), Υ_(CP) is the polar aspect ofcoating/layer 3; Υ_(LD) is the dispersive aspect of liquid (e.g. water),and Υ_(CD) is the dispersive aspect of coating/layer 3. It is noted thatadhesion energy (or effective interactive energy) W, using the extendedFowkes equation, may be determined by:

W=[Υ_(LP)*Υ_(CP)]^(1/2)+[Υ_(LD)*Υ_(CD)]^(1/2)=Υ_(l)(1+cos θ),

[0062] where Υ_(l) is liquid tension and θ is the contact angle. W oftwo materials (e.g. layer 3 and water thereon) is a measure ofwettability indicative of how hydrophilic the layer or coated articleis.

[0063] When analyzing the degree of hydrophilicity of layer 3 or acoated article herein with regard to water, it is noted that for waterΥ_(LP) is 51 mN/m and Υ_(LD) is 22 mN/m. In certain embodiments of thisinvention, the polar aspect Υ_(CP) of surface energy of layer 3 is atleast about 5, and more preferably at least about 7, and most preferablyfrom about 7-10 (variable or tunable between 5 and 15 in certainembodiments) and the dispersive aspect Υ_(CD) of the surface energy oflayer 3 is from about 16-22 mN/m (more preferably from about 18-20mN/m).

[0064] Using the above-listed numbers, according to certain embodimentsof this invention, the surface energy Υ_(C) of layer 3 is at least about24 mN/m, more preferably at least about 26 mN/m, and most preferably atleast about 28 mN/m; and the adhesion energy W between water and layer 3is at least about 600 mN/m, more preferably from about 700-1,300 mN/m,even more preferably from about 750-950 mN/m, and most preferably fromabout 800-950 mN/m. These high values of adhesion energy W and layer 3surface energy Υ_(C), and the low initial contact angles θ achievable,illustrate the improved hydrophilic nature of coated articles accordingto different embodiments of this invention.

[0065] The initial contact angle θ of a conventional glass substrate 1with sessile water drop 31 thereon is typically from about 22-24degrees, as illustrated in FIG. 4 (although it may be as low as 18degrees in certain instances). Thus, conventional glass substrates arenot as hydrophilic as embodiments of this invention. Moreover, layers 3herein provide for scratch resistance and/or high durability. A normalta-C layer, undoped, on a glass substrate is not as hydrophilic asembodiments of this invention. Inventions herein enable the contactangle of a ta-C inclusive layer 3 to be reduced to improve thehydrophilicity of a coated article, as shown by the low contact angle θin FIG. 6.

[0066] Another advantage associated with certain layers 3 according tocertain embodiments of this invention is that the layer 3 may becomeelectrically conductive so as to reduce the likelihood of a build-up ofstatic electricity. This reduction in resistivity is believed to be dueto the doping described herein. For example, prior to doping resistivityof a ta-C layer may be, e.g., 10⁸ ohms/cm, whereas after doping theresistivity may drop to, e.g., less than about 500 ohms/cm, morepreferably less than about 100 ohms/cm, most preferably from about 0.01to 50 ohms/cm.

[0067] Layer 3 may have a dielectric constant of from about 8 to 12 at10 kHz, preferably about 10, and may have a dielectric constant of about2 to 6 at 100 MHz, preferably about 4. In certain embodiments, layer 3may have an electrical breakdown strength (V cm⁻¹) of about 10⁶. As forthermal properties, layer 3 may have a thermal coefficient of expansionof about 9×10⁻⁶/C, and a thermal conductivity of about 0.1 Wcm K.

[0068]FIGS. 7-8 illustrate an exemplary linear or direct ion beam source25 which may be used to deposit layer(s) 3, clean a substrate 1, orsurface plasma treat a DLC inclusive layer to add doping atoms theretoaccording to different embodiments of this invention. Ion beam source 25includes gas/power inlet 26, racetrack-shaped anode 27, grounded cathodemagnet portion 28, magnet poles 29, and insulators 30. A 3 kV DC powersupply may be used for source 25 in some embodiments. Linear source iondeposition allows for substantially uniform deposition of DLC inclusivelayer 3 as to thickness and stoichiometry.

[0069] Ion beam source 25 is based upon a known gridless ion sourcedesign. The linear source is composed of a linear shell (which is thecathode and grounded) inside of which lies a concentric anode (which isat a positive potential). This geometry of cathode-anode and magneticfield 33 gives rise to a close drift condition. The magnetic fieldconfiguration further gives rise to an anode layer that allows thelinear ion beam source to work absent any electron emitter. The anodelayer ion source can also work in a reactive mode (e.g., with oxygenand/or nitrogen). The source includes a metal housing with a slit in ashape of a race track as shown in FIGS. 7-8. The hollow housing is atground potential. The anode electrode is situated within the cathodebody (though electrically insulated) and is positioned just below theslit. The anode can be connected to a positive potential as high as3,000 volts. Both electrodes may be water cooled in certain embodiments.

[0070] Feedstock gases are fed through the cavity 41 between the anodeand cathode. The linear ion source also contains a labyrinth system thatdistributes the precursor gas evenly along its length and which allowsit to supersonically expand between the anode-cathode space internally.The electrical energy then cracks the gas to produce a plasma within thesource. The ions are expelled out and directed toward the substrate 1 onwhich the layer(s) 3 is to be grown. The ion beam emanating from theslit is approximately uniform in the longitudinal direction and has agaussian profile in the transverse direction. Exemplary ions 34 areshown in FIG. 7. A linear source as long as 0.5 to 3 meters may be madeand used, although sources of different lengths are anticipated indifferent embodiments of this invention. Electron layer 35 is shown inFIG. 7 and completes the circuit thereby enabling the ion beam source tofunction properly.

[0071] Exemplary methods of depositing a DLC inclusive hydrophilic layer3 over top of and on a substrate 1 (the substrate may have otherlayer(s) (e.g., layer 2) already provided thereon) will now bedescribed. These methods are for purposes of example only and are notintended to be limiting. The energies used during the deposition processof layer 3 and/or the directionality provided by the ion beam depositiontechniques enable layer 3 to be fairly uniformly deposited over allaspects of the underlying structure.

[0072] Prior to layer 3 being formed on substrate 1, the top surface ofsubstrate 1 may be cleaned by way of a first linear or direct ion beamsource. For example, a glow discharge in argon (Ar) gas or mixtures ofAr/O₂ (alternatively CF₄ plasma) may be used by the source to remove anyimpurities on the substrate surface. Preferably, no oxygen orfluorocarbons are used since in the next step doping with N and/or Batoms takes place. Such interactions are physio-chemical in nature. Thepower density may be, for example, 1 Watt/cm². Substrate 1 may also becleaned by, for example, sputter cleaning the substrate prior to actualdeposition of layer 3. While cleaning may be performed in someembodiments, it need not be performed in other embodiments of thisinvention.

[0073] Then, the deposition process for DLC inclusive layer 3 onsubstrate 1 may be performed using the linear ion beam source andcorresponding deposition technique as illustrated in FIGS. 7-8 (e.g.,see linear ion beam 25). The ion beam source 25 (which may be the sameor a different source than the cleaning ion beam source) functions todeposit a ta-C inclusive layer 3 (hydrogenated in certain embodiments)on substrate 1, along with dopants (e.g., N and/or B) therein. Exemplaryfeedstock gases which may be used include Nitrogen gas, diborane gas,and/or C₂H₂ gas.

[0074] Alternatively, layer 3 may be deposited using a filtered cathodicvacuum arc ion beam apparatus (FCVA-IB) as disclosed in “TetrahedralAmorphous Carbon Deposition, Characterisation and ElectronicProperties”, by Veerasamy, Cambridge 1994 (incorporated herein byreference). This deposition process may be achieved just after a plasmaclean of the substrate 1 using the same deposition chamber, or anotherchamber. In such techniques, a cathodic arc discharge of an ultrapurecarbon target may be triggered in a base vacuum of, e.g., <10⁻⁶ Torr. Atarget consisting essentially of Hoescht carbon may be machined into acylindrical electrode about 90 mm in diameter and about 50 mm deep.Conditions of arc discharge may be, e.g., 70 A and 17 V. The pressureduring the cathodic arc process may be in the range of a tenth of amTorr. One, two, or more dopant gas(es) may be simultaneously introducedinto the toroidal bend region. Exemplary gases may be diborane(including a dopant B) and Nitrogen. Gas flows may be controlled by twomass flow controllers in series with a needle valve. The diborane gasmay be independently flowed through such a controller. The power iscoupled by plasma collisions to the dopant gas diborane and Nitrogenmixture which may be introduced via a mass flow controller at the bendof the magnetic filter. An exemplary torroidal magnetic field may be 100mTesla. The energetic carbon ions and high energy electrons togetherwith the UV radiation produced by the arc dissociate(s) the gas mixtureinto extremely reactive energetic ions. In general, only ionized species(e.g., C, N, and B) are constrained to follow the toroidal magneticfield in the filter while the neutrals and macroparticles are filteredout. The flux of ionized atoms is/are transported to the growth surfaceon the substrate 1 so that layer 3 is formed. The ion energy can beindependently varied by a grid which has a negative potential or RF biason the substrate to tune the physical properties of the layer 3. Therange of self bias potential is from, for example, −1,000 to +1,000 V.In certain embodiments, a window of 120-200 V per ion species may beused. Partial pressures used during the deposition may be, for example,from 10⁻⁶ to 10⁻⁴ Torr. Exemplary parameters which may be used in such adeposition process are: base pressure of 10⁻⁶, N₂ gas 0-5 sccm, B₂H₄ gas0-2 sccm, a room temperature for substrate 1, and an arc power of 1,000W. In such a manner, layer 3 including amorphous DLC doped with B and/orN may be formed on substrate 1.

[0075] The hydrophilic nature of layer 3 may be enhanced in certainembodiments by using a plasma treatment or grafting procedure which addscertain polar functional groups at the surface of layer 3, altering thechemical reactivity at the surface while the bulk properties of thelayer remain substantially unaffected. In such embodiments, a plasma ofNitrogen gas (N₂) may be used at a pressure of about 1 mT to enhance thehydrophilic nature.

[0076] In one instance, ta-C films having thicknesses from 10 to 50 nmwere deposited on quartz substrates with an interdigitated planar arrayof 20 μm Ni electrodes. These electrodes were prepared by conventionallithographic techniques. The influence of the adsorbed molecules on theelectrical properties of the ta-C doped films were then studied usingI—C—V characteristics. Strong sensitivity of the I—C—V characteristicswere found in the presence of water and alcohol. The high sensitivity ofthe capacitance on water vapor concentration as well as the quickresponse to water molecules suggested a high polar component of thesurface bonds. A layer 3 of ta-C:N:B also has a high density asevidenced by its high plasmon peak at about 32.9 eV.

[0077] When it is desired to hydrogenate layer 3, for example, a dopantgas may be produced by bubbling a carrier gas (e.g. C₂H₂) through theprecursor monomer (e.g. TMS or 3MS) held at about 70 degrees C (wellbelow the flashing point). Acetylene feedstock gas (C₂H₂) is used incertain embodiments to prevent or minimize/reduce polymerization and toobtain an appropriate energy to allow the carbon and/or hydrogen ions topenetrate the article and subimplant therein, thereby causing the layer3 to grow. Other suitable gases, including polar inducing dopant gases,may also be used in the source to create the ions 34.

[0078] As mentioned above, in addition to doping, it has been found thatthe layer 3 may be made more hydrophilic in nature as a function of howit is deposited on substrate 1. The temperature of substrate 1 may beraised during the deposition process (e.g., to about 100-300 degreesC.). An alternative way in which to make the layer more hydrophilic isto increase the ion energy used during the deposition process, e.g., toabout 200 to 500 eV, most preferably about 400 eV, in order to reducesp³ bonding content in the layer 3. In other embodiments of thisinvention (doping and/or UV exposure embodiments), a base portion oflayer 3 may be ion beam deposited at a rather high ion energy (e.g.,750-1500 eV per two C atoms) and then for deposition of the top portionof the layer 3 the ion energy is lowered to a lower level (e.g., from10-200 eV per two C atoms) to provide more sp² C—C bonds at the surfaceof layer 3.

[0079] While ion beam deposition techniques are preferred in certainembodiments, other methods of deposition may also be used in differentembodiments. For example, filtered cathodic vacuum arc ion beamtechniques may be used to deposit layer 3 as discussed above. Moreover,sputtering techniques may also be used to deposit layer 3 on substrate 1in other embodiments.

[0080]FIG. 9 is a flowchart illustrating steps taken according toultraviolet (UV) exposure embodiments of the instant invention (whichmay or may not be doped in different embodiments of this invention).Initially, a DLC inclusive layer 3 is ion beam deposited on a substrate1 in step S1. The DLC inclusive layer 3 may or may not be doped asdescribed above. Other than the potential for not being doped, DLCinclusive layer 3 is as described in any of the aforesaid embodiments ofthe instant invention. Layer 3 as originally deposited may or may not behydrophilic; e.g., the layer 3 may have a contact angle θ anywhere inthe range of from 5-100 degrees. The DLC inclusive layer 3 may bedeposited directly on substrate 1 (see FIG. 1), or alternatively on thesubstrate 1 over another layer(s) as described above (see FIG. 3).Following deposition of DLC inclusive layer 3, the layer 3 is exposed toUV radiation/rays in step S2. This exposure to UV radiation may becarried out during the process of manufacture (e.g., a UV source foremitting UV rays toward layer 3 may be located on an apparatus followingthe ion beam source used for depositing layer 3), and/or alternativelythe UV exposure may take place in ambient atmosphere (e.g., letting thecoated article with layer 3 thereon sit outside in the sun/rain). Ineither case, the DLC inclusive layer 3 is exposed to UV radiation whichcauses the contact angle θ of the layer 3 to decrease. Optionally, watermay be applied to the layer 3 during the UV exposure to speed up thecontact angle reducing process. The resulting decrease in contact angleθ is illustrated in step S3.

[0081] It is noted that UV A seems to work well is exposing the layer 3to cause decrease in contact angle. The “A” type (lower energy) of UV iswavelengths in the range of from 315-380 nm (near UV). Following and/orduring UV exposure, the film remain scratch resistant and hard (e.g.,even after 600 hrs. QUV), and film thickness does not substantiallychange (i.e., does not change by more than 0-5%).

[0082] It is believed that UV exposure of the DLC inclusive layer 3results in oxidation and causes a thin carbon-oxide layer/portion toform at the surface of the layer 3 (e.g., including —C═O and/or O—C═Obonds). This thin at least partially oxidized surface layer portion hasa fair amount of attraction to water molecules (polar bonds), thusexplaining its hydrophilicity. This thin carbon oxide inclusivelayer/portion may be from about 1-30 Å thick, more likely/preferablyabout 5-15 Å thick (in this regard, the high frequency of dots in layer3 in FIG. 2 can be used to represent this thin carbon oxide portion atthe top surface of overall layer 3; in a sense the UV is causing the DLClayer 3 surface to become doped with oxygen). This thin carbon oxideportion is believed to seal off the remainder of the layer 3 from theambient atmosphere, so as to prevent further oxidation (i.e., the bulkof the hard sp³ carbon-carbon bonds in the bulk of the layer 3 are thusresistant to oxidation so that the layer maintains its scratchresistance and the like). This sealing off prevents degradation of thebulk of layer 3, while at the same time providing hydrophilic properties(i.e., low contact angle). The layer upon UV exposure also has lesspropensity for dust to be attracted thereto.

UV EXPOSURE EXAMPLE

[0083] The following Example was performed for purposes of illustratingone non-limiting implementation of a UV exposure embodiment of thisinvention pursuant to FIG. 9. On a 2 mm thick clear glass substrate, aDLC layer 3 was ion beam deposited to a thickness of 14.69 angstroms (Å)using acetylene (C₂H₂) feedstock gas (145 sccm) at a linear velocity of100 inches/minute, at 2970 V and 0.57 amps. The layer 3 was not dopedwith any of the dopants B, N, etc. above. The results was a DLC layer 3of a-taC:H, having an initial contact angle θ of 73.47 degrees. Then,the coated article was QUV exposed for 86 hours (combination of UVradiation and water). The QUV machine was set for cycles of two (2)hours heat (about 60 degrees C.) and humidity (i.e., water) followed bytwo (2) hours of UV light exposure (the UV light/radiation was fromUVA-340 fluorescent bulbs that match the UV spectrum of sunlight aswell). Following the QUV exposure, the coated article includingsubstrate 1 with DLC layer 3 thereon had a contact angle θ which haddropped all the way down to 19.12 degrees; Thus, it can be seen that thecontact angle decreased by about 74% (i.e., 73.47−19.12=54.35; and54.35/73.47=0.7398 or about 74%). Further UV exposure would allow thecontact angle to drop even further. Thus, the DLC layer 3 as depositedwas not hydrophilic, but after significant UV exposure the contact angleθ of the article had dropped down into the hydrophilic range (i.e., lessthan 20 degrees). It can be seen that the UV exposure caused the contactangle of the layer 3 to significantly drop into the hydrophilic range of<=20 degrees.

[0084] In certain example embodiments of this invention, the DLCinclusive layer 3 is exposed to UV radiation (and optionallywater/humidity) in a manner (e.g., amount of UV exposure) sufficient tocause the contact angle θ of the layer 3 to decrease by at least about20%, more preferably by at least about 30%, even more preferably by atleast about 50%, and in certain cases (see Example above) by at leastabout 70%.

[0085] It is noted that The term “QUV” herein means that the coatedarticle is exposed to UV radiation and water, using a QUV AcceleratedWeathering Tester available from “The Q-Panel Company, Cleveland, Ohio”to simulate sunlight/rain/humidity. This QUV machine exposes the coatedarticle to UV radiation/light using fluorescent UV lamps, and simulatesrain and dew with condensing humidity. Coated articles are tested usingQUV by exposing them to alternating cycles of light and moisture atcontrolled, elevated temperatures (typically from 50-90 degrees C.).During the condensation cycle, a water reservoir in the bottom of thetest chamber is heated to produce vapor; and the hot vapor keeps thechamber at about 100% relative humidity.

[0086] Advantages of certain embodiments of this invention include, forexample, any advantage listed above, the hydrophilic nature of thearticle/layer, the ability of the layer 3 to withstand high temperatureswithout burning, the reduction of resistance so as to reduce thelikelihood of static buildup, the fact that the deposition process maybe performed at low temperature(s) such as room temperature in certainembodiments, the high deposition rates which may be used (e.g., >2nm/s), the fact that the deposition process is scalable to large areadeposition (e.g., >1 square meter), the high throwing power of thedeposition apparatus in its capability of coating to within 5-8% oncurved surfaces of a substrate 1, the smooth nature of layer 3 absentmany if any pinholes, the ability to realize conformal growth of layer3, the ability to use layer 3 in combination with other underlyinglayers such as low-E layers or silicon nitride layers or silicon oxidelayers, and/or the ability to tune the layer's properties by varying theion energy and/or gases used during the deposition process.

[0087] Once given the above disclosure, many other features,modifications, and improvements will become apparent to the skilledartisan. Such other features, modifications, and improvements are,therefore, considered to be a part of this invention, the scope of whichis to be determined by the following claims.

1-30. (Canceled)
 31. A method of making a coated article, the methodcomprising: forming a layer comprising diamond-like carbon (DLC) on asubstrate; and exposing the layer comprising DLC to ultraviolet (UV)radiation so that the layer comprising DLC has a contact angle θ of lessthan or equal to 20 degrees.
 32. The method of claim 31, wherein thelayer comprising DLC is formed using an ion beam.
 33. The method ofclaim 31, wherein the layer comprising DLC has a contact angle of lessthan or equal to 15 degrees.
 34. The method of claim 31, wherein thelayer comprising DLC has a contact angle of less than or equal to 10degrees.
 35. The method of claim 31, wherein the layer comprising DLC ision beam deposited in a manner so as to include hydrogen.
 36. The methodof claim 31, wherein the layer comprising DLC has an average hardness ofat least 10 GPa.
 37. The method of claim 31, wherein the layercomprising DLC has an average hardness of at least 20 GPa.
 38. Themethod of claim 31, wherein the layer comprising DLC is provided on thesubstrate, so that a low-E coating is located between the substrate andthe layer comprising DLC.
 39. The method of claim 38, wherein the low-Ecoating comprises at least one layer comprising silver.
 40. The methodof claim 31, wherein the coated article is a window having a visibletransmittance of at least 60%.
 41. The method of claim 31, wherein thelayer comprising DLC includes sp³ carbon-carbon bonds.
 42. The method ofclaim 31, wherein said exposing of the layer comprising DLC to UVradiation causes the contact angle of the layer comprising DLC todecrease by at least about 20%.